Conventionally, in film forming apparatuses or etching apparatuses such as PVD apparatuses, CVD apparatuses, ion plating apparatuses, and vapor deposition apparatuses, in order to precisely immobilize a work piece such as a silicon wafer, the work piece is forcedly adsorbed to a flat and smooth finished surface of a plate-like member. As adsorption means for this purpose, an electrostatic chuck utilizing an electrostatic adsorptive force is used.
Such an electrostatic chuck used in these film forming apparatuses or etching apparatuses includes: an adsorption face that is formed as one of the main faces (one of the largest faces) of a plate-like insulating substrate made of ceramics; and an adsorption electrode that is inside the insulating substrate or on another main face (another largest face) of the insulating substrate; wherein an electrostatic adsorptive force is generated such as a Coulomb's force due to dielectric polarization or a Johnsen-Rahbek force due to a slight leakage current between the electrostatic chuck and a work piece through the application of a DC voltage to the adsorption electrode, thereby causing the work piece to be forcedly adsorbed and immobilized to the adsorption face.
In the electrostatic chuck, a lifting pin for detaching the work piece from the adsorption face is disposed so as to be freely projected from a peripheral portion of the adsorption face corresponding to a peripheral portion of the work piece.
Here, in a conventional electrostatic chuck used for plasma treatment, it is known that a so-called residual adsorption appears in which an adsorptive force is left even after DC voltage application to the adsorption electrode is cancelled. This residual adsorption appears in such a manner that fixed electric charges (positive holes) are generated on an insulating substrate when electrons are injected from plasma to the work piece, and, even after the DC voltage is turned off, the fixed electric charges (positive holes) are left on the insulating substrate.
Here, there has been a problem that, when an attempt is made to detach the work piece from the adsorption face using a lifting pin in a state where the residual adsorptive force is large, the work piece is deformed or damaged.
In order to address this problem, there has been a known method for removing fixed electric charges by performing plasma exposure (electron injection) with sufficient time in a state where the DC voltage is off. Furthermore, an electrostatic chuck has been proposed that has a stress sensor for detecting stress applied to a lifting pin and controls movement of the lifting pin (see Patent Literature 1). It is possible to suppress a work piece from being deformed or damaged by using this fixed electric charge removing method and this electrostatic chuck.